1. Field of the Invention
The present invention relates to an electronic organ having an improved system for generating tone signals, and more particularly, pertains to an organ system wherein digital logic circuitry controls programmable generators and a network of gates so as to produce the tones called for by the played notes of the organ, while minimizing the actual number of generators required to produce the desired musical effect.
2. Description of the Prior Art
The prior art teaches the use of conventional diode keying techniques where each gate receives a single input signal of a specified frequency, and an associated key switch on the keyboard controls the gate. The key switches of the keyboard may control gates of various footages, in accordance with the voices made available by the organ. Accordingly, in prior art systems there must be a separate gate for each note of each manual, and for each footage which can be played by such note. For example, an organ with two 44-note manuals having 8-foot and 4-foot voices on each, would require 176 separate gates.
This form of conventional diode keying is shown by way of example in U.S. Pat. No. 3,223,768 to Munch, et al. and U.S. Pat. No. 3,580,980 to Uetrecht, both assigned to the same assignee as the present invention.
An alternative tone generator system is taught in U.S. Pat. No. 3,515,792 to Deutsch which shows a generator system using stored digital representations of pipe organ wave forms. In the Deutsch system, wave forms characteristic of particular organ voices are stored in a digital format. Recycling read controls 22A through 22N read out the stored wave forms at speeds dictated by frequency synthesizer 10. In this manner, each recycling read control can cause one note to be produced. It should be noted, however, that octavely related notes cannot be produced simultaneously by a single recycling read control. Rather, the Deutsch system requires a separate recycling read control for each note to be sounded, regardless of whether the notes are octavely related. As a result, the Deutsch system is only capable of sounding as many notes at one time as there are recycling read control circuits.